The invention relates to an air nozzle for drying a fabric web supported on supporting means, comprising a nozzle head which is arranged transversely in relation to the fabric web, and which has a number of rows of adjacent nozzle holes extending in the nozzle head direction, and located on the side facing the fabric web.
In a known nozzle arrangement of this kind, the discharge direction of each nozzle hole is parallel, and perpendicular to the fabric web, or the jets are inclined towards one another, so that a high static pressure is produced between the air nozzle and the fabric web. This high static pressure causes a steep pressure gradient at the edges of the air nozzle, with the result that the air blast is discharged at a high speed from the area between the fabric web and the sir nozzle, thus allowing suction forces to act on the fabric web. The suction forces load the fabric web, depending on its properties, either to a greater or lesser degree, and pull it towards the air nozzle (aerofoil effect), which decreases the discharge cross-section, and further increases the discharge rate and hence the suction forces. Webs of material, which have low stability of shape and tensile strength (e.g. woven goods still wet from printing, non-woven fabric, mica pulp, paper pulp), and which are therefore transported through the air-blast area of the air nozzle on a travelling base as carrier, e.g. a belt or roller, do not tolerate aerodynamic loading, or only low aerodynamic loading. This is because tensile stress can lead to tearing of the fabric web, or lift-off of the web whilst the woven goods are still wet from printing, which can involve the danger of the print becoming smudged, and therefore, up till now, the suction forces acting on the fabric web have been kept as low as possible, by maintaining a low speed of air blast by reducing the rate of the air supply. However, with this method it was also accepted that the degree of drying which is directly dependent on the air blast quantity, deteriorated.